I have a few Nonpareils, and can offer you some general information which might help you roughly date the pipe. I am speaking from memory and have not reviewed this issue for some time, so please forgive me if I any of this turns out to be slightly off base. There are two very rough ways to date nonpareils (and I do mean rough, as in by decade). First, they have not made that model in a smooth finish for some time - I believe not since the 80's. Second, they were originally made with a horn ring, but that later changed to lucite. I believe that I own at least one of each, and frankly it is hard to tell which is which. I believe that the earlier, horn models had a metal ring instead of the later plastic one on the inside. Second, the horn develops microcracks or seams which the lucite does not develop.
The numbers correspond to specific shapes, and they only offered these pipes in a limited number of shapes. There are a selection of these in the 1979 Iwan Reis catalog that you can see on Chris' pipe pages, as one of their house brand pipes, but they identify them as nonpareils made for them by Savinelli. They were charging $80.00 for them back then (probably a little cheaper than the genuine Savinelli), and identified them as still having the horn ferrule.
They are really nice pipes, and smoke very well. My only gripe, as with all Savinelli's, is that the briar quality declined significantly as the years went by, and this is noticeable in the later smooth finish pipes, where they began to sneak fills in and allowed other imperfections which were not present on the earlier pipes.
You did a great job on the clean-up. The only word of caution that I would offer is to not use the sand paper now that you have the oxidation off. These are thin bits and you will wear down the vulcanite. You can buy really nice pipe stem cleaner from walker briar works which will take off the oxidation but is much less abrasive. Now that you have it clean, use a thin coat of plain carnuba wax (also available from Walkers), or, at a minimum, use the spray briar wipe that you spray on a cloth first, and allow to dry, and then you can use the cloth for several months. I use both - the carnuba once in a while, and the impregnated cloth after every smoke. You should not have any problems with oxidation. With the carnuba, you use it just like on your car - put it on, let it dry, and then buff it off. Finally, I use a rubber bit on every pipe. I guess my teeth are sharp because I leave marks without them, no matter how lightly I smoke. They allow you to hold the pipe in your mouth without worrying about biting through eventually.
Good luck, and enjoy your pipe. Now you just need a sandblast finish to match it! (and then a straight in the smooth finish, and then one of each shape, etc, etc.)